Author Topic: High pitched chitter - where from?  (Read 948 times)

High pitched chitter - where from?
« on: March 19, 2017, 04:25:29 pm »
My 2 speed Brompton has developed a high pitched chitter, up there with chalk on blackboard - but definitely chittery, whenever/ not always (but I can induce it 90% of the time) I go over rough tarmac, speed bumps, potholes, drain covers etc.
It is coming from the front end of the bike, and as I say it it chittery, rather than cyclical.
It has that dry metal on dry metal flavour to it.
I thought it might be from the points of contact between the main hinge clips and the frame (I have the Brompification variety) so I've given the mating surfaces of both some lithium grease - with little or no effect - which makes me think a) Try Copaslip and b) it is something else.
Anyone else experienced anything similar?
It isn't a high mileage bike and has hardly ever been out in the rain.

LittleWheelsandBig

  • Whimsy Rider
Re: High pitched chitter - where from?
« Reply #1 on: March 19, 2017, 05:16:08 pm »
Have a close look at the handlebars, including under the clamp. Mostly from consequences, rather than likelihood.

Possibly front brake cable on mudguard?
Wheel meet again, don't know where, don't know when...

Re: High pitched chitter - where from?
« Reply #2 on: March 19, 2017, 05:25:10 pm »
Have a close look at the handlebars, including under the clamp. Mostly from consequences, rather than likelihood.

Possibly front brake cable on mudguard?
Good call with the handlebars - will investigate.
Noise is too 'weighty/defined' to be cable on mdgrd.

Re: High pitched chitter - where from?
« Reply #3 on: April 01, 2017, 02:32:13 pm »
So, who wants to know where the chitter was coming from?
Instinct, instinct, instinct.
Always go with it.
Unless you have form for being wrong.  :P
It wasn't the main hinge, but it was the mating surfaces of the hinge in the bars / stem.
I applied a little grease to both and the chittering was slightly reduced.
I subsequently applied a MkI section of inner tube, thusly:
 
and it is totally silent.
Like a nun's fart.
Not yet sure what I am going to do as a long term solution which is maintenance minimum, or preferably, free - but at least it appears that I have identified the source of the chittering.

Re: High pitched chitter - where from?
« Reply #4 on: April 01, 2017, 02:38:29 pm »
There are a lot of Chiffchaffs about now. One nesting in the stem?

Re: High pitched chitter - where from?
« Reply #5 on: April 01, 2017, 02:44:01 pm »
Either that or a hamster on its wheel.

Adam

  • It'll soon be summer
    • Charity ride Durness to Dover 18-25th June 2011
Re: High pitched chitter - where from?
« Reply #6 on: April 04, 2017, 09:18:01 pm »
Not yet sure what I am going to do as a long term solution which is maintenance minimum, or preferably, free - but at least it appears that I have identified the source of the chittering.

How about cutting down in size one of those little self adhesive pads you get to stick on drawers to stop bangs as they close?
“Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

LittleWheelsandBig

  • Whimsy Rider
Re: High pitched chitter - where from?
« Reply #7 on: April 04, 2017, 09:45:07 pm »
Remove the powder coating from the contact points?
Wheel meet again, don't know where, don't know when...

Kim

  • An appetite for the epic, but no real stamina
Re: High pitched chitter - where from?
« Reply #8 on: April 04, 2017, 09:50:29 pm »
Not yet sure what I am going to do as a long term solution which is maintenance minimum, or preferably, free - but at least it appears that I have identified the source of the chittering.

How about cutting down in size one of those little self adhesive pads you get to stick on drawers to stop bangs as they close?

I'm wondering about PTFE mouse feet...  (Or just normal stick-on rubber feet.)
Watching the TV without subtitles is like riding up a hill without using the gears :)

Re: High pitched chitter - where from?
« Reply #9 on: April 04, 2017, 10:46:25 pm »
Perhaps the aluminium section of the clamp needs replacing. Supposedly they 'spread' over time. Ah, hang on, it looks as though you're using a third party version. I've been reluctant to use those as they appear to lack the slight curvature or central bulge of the Brompton version, which makes sure the clamping force is focused on the edge areas.

Re: High pitched chitter - where from?
« Reply #10 on: April 05, 2017, 06:41:13 am »
Copied from another place, after someone's suggestion that the clamp was bottoming-out before full clamping force had been achieved:

Today's activities:

1) Remove the Brompification handlebar clamp and try to measure the width of the jaw - difficult as it has asymmetric legs and they have a radius with no definitive edge to measure from.

2) Place same clamp in 3" vice (the 5" one is somewhere under the stairs and I can't be arsed) and using a 450mm tommy bar, crush the clamp in the vice to try and reduce the width of the jaw. Using my digi-verniers, I may have reduced the width by 0.3mm. Or by nothing.

3) Replace clamp on bike and go for a ride which reveals reduced, but still-present chitter.

4) Dig out original Brompton clamp from storage, fit to bike, go for a ride which ascertains there is no audible reduction in chitter.

5) Remove Brompton clamp from bike, measure the width of the jaw and put it in the crusher.

6) Re-fit crushed Brompton clamp to bike, go for a ride which ascertains there is no further audible reduction to chitter. It is reduced, but it is still there.

7) Decide to re-fit Brompification clamp, and supplement it with MkI inner tube (see above) as this seems to be the only way I can achieve a chitter-free ride.

I can't help but think that there is a correlation between chitter manifesting itself, and the wearing-away of the powdercoat from the mating surfaces of the hinge - giving it a
metal-on-metal scenario - which on a three year old bike, which has hardly seen any use other than the occasional weekend - is probably about right.

Unless, of course, anyone has any better ideas.

Re: High pitched chitter - where from?
« Reply #11 on: April 05, 2017, 10:40:38 am »
a strip or two of silicone sealant applied to a hinge surface?

Re: High pitched chitter - where from?
« Reply #12 on: April 05, 2017, 12:47:33 pm »
a strip or two of silicone sealant applied to a hinge surface?
Now that's an idea I wish I'd had myself - I'll be giving that a go to see whether it is more resiliant than the MkI inner tube damper.
It isn't a big deal to carry half a dozen pre-cut inner tubes on the bike - they will, I think, wear through in fairly short order - but it'd be nice, having applied a remedy,  not to have to do anything at all.

Re: High pitched chitter - where from?
« Reply #13 on: April 05, 2017, 12:53:50 pm »
Some tubeless rim tape might work well as it's thin, tough and very sticky - Stans, Tesa 4289, gorilla tape or similar.

Re: High pitched chitter - where from?
« Reply #14 on: April 05, 2017, 01:00:15 pm »
My aluminium Dahon creaked all over whereas my steel Brompton doesn't at all (except the suspension block). Those contacting areas always end up as bare metal but I've not heard anyone else talk of noise. Perhaps the spindle/hinge is worn and the surfaces are sliding as a result?

Re: High pitched chitter - where from?
« Reply #15 on: April 05, 2017, 01:09:53 pm »
Some tubeless rim tape might work well as it's thin, tough and very sticky - Stans, Tesa 4289, gorilla tape or similar.

That's handy  - I have Tesa 4289 coming out of my ears, here at work  :thumbsup: (and, perhaps unsurprisingly, some at home  ;))

I think the trick there might be to leave the backing tape on -  if I cleaned up the mating surfaces with isoprop, and put 4289 on them - I could probably throw away the clamps....

I also have some VHB tapes from 3M which might suit this task even better - I understand the aircraft industry uses them for bonding skins onto wings of airliners.

Re: High pitched chitter - where from?
« Reply #16 on: April 05, 2017, 01:16:39 pm »
The 4289 I've got is single-sided, but leaving one backing strip on would probably be almost as good.

Re: High pitched chitter - where from?
« Reply #17 on: April 05, 2017, 08:03:21 pm »
I've just de-greased the mating faces of the stem hinge, cleaned them with isoprop and applied the Tesa 4289 to both mating surfaces - leaving the backing tape on, it has a nice viscous feel to it - so that's good.
Been for a short test ride, and all is silent.
I'm interested to see (or hear) how the longevity of this arrangement works out.